Of the principal characteristics that nail polishes should possess, the following may be singled out in particular: good adhesion to the nail surface, and a certain flexibility and strength of the film to prevent its fragility leading to cracking of the polish.
In general, at the present time, modified resins are used to confer good adhesion and plasticizers to lead to good flexibility of the polish.
After a substantial volume of research, it has not been found that good adhesion of a colorless or colored polish to the nail surface as well as good strength can be obtained by incorporating certain fibers.
British Patent No. 1,177,420 has already proposed polishes for reinforcing and repairing broken nails, containing 0.5 to 12% of certain fibers such as for example fibers of silk, cotton, nylon, polyacrylonitrile, polyethylene terephthalate, and other polymers or copolymers.
According to this patent, the fibers present in the polish act as a nail-reinforcing agent but do not favor adhesion or strength of the polish on the nail at all.